imo has no doubt gotten a bit of boost in the last couple of months, when Meebo finally shuttered its Messenger offering ahead of its social-boosting Google integration, and now the service is getting a bit more robust for iOS users. The instant messaging aggregator (AIM, Google Talk, Facebook chat, et al.) is bringing free voice calling to iPhones running iOS version 3.1 and higher, a feature already available on its Android offering.